1. Field of the Invention
This invention relates to a tip cap for closure of the opening of a liquid filled container, and more particularly, to a tip cap for a syringe.
2. Description of Related Art
Conventional syringes include a barrel having an open proximal end and an opposed distal end. A cylindrical wall extends between the ends and defines a substance retaining chamber. A tip, sometimes referred to as a luer, projects from the distal end of the syringe barrel and includes a narrow passage, which communicates with the substance-retaining chamber of the barrel. A plunger is inserted into the open proximal end of the syringe barrel for sliding fluid-tight engagement with the cylindrical chamber wall. Sliding movement of the plunger in a distal direction urges fluid in the chamber through the passage in the tip. Conversely, sliding movement of the plunger in a proximal direction draws fluid through the passage in the tip and into the chamber of the syringe barrel.
Such syringes may further include a needle assembly with a needle cannula having a proximal end, a pointed distal end and a lumen extending axially therethrough. The needle assembly commonly includes a hub which is securable to the syringe barrel for selectively placing the lumen of the needle cannula in fluid communication with the passage through the tip of the syringe barrel. The needle assembly may be removably or fixedly mounted to the tip of the syringe barrel.
Medications that are pre-filled into a syringe barrel must be sealed to prevent contamination or loss of the medication prior to use. Seals also prevent health care workers from being needlessly exposed to medications. Where a needle is not staked to the syringe body, the prior devices have included stoppers or closures mounted over the tip at the distal end of the syringe barrel, referred to as tip caps, to prevent leakage and to avoid contamination of the medication. When a pre-filled syringe is capped with a tip cap, it is especially important that a good seal be maintained. This is usually achieved by tightly affixing the tip cap to the syringe. However, when overly tightened the tip cap can be difficult to remove or may be damaged. Furthermore, a pre-filled syringe may be autoclaved after filling and capping to ensure a sterile package for the contents. The autoclaving procedure however, can also have the side effect of interactions between the tip cap to the syringe, thereby further increasing the difficulty in removing the cap.
The prior art tip cap is removed from the syringe tip shortly prior to usage of the syringe, and the hub of the needle assembly is securely engaged with the luer and/or luer collar or other mounting means adjacent the exposed tip of the syringe barrel. For example, the needle hub may be threadedly engaged within a luer collar such that the lumen of the needle cannula communicates with the exposed tip of the syringe barrel, such as with the configuration sold by the assignee herein under the trademark “Luer-Lok”.
Current tip caps used to seal the liquid opening of the syringe barrel, are typically a one-piece design having a circular cap wall design. The mechanical advantage of a screw-type threaded cap is translation of a rotational force to an axial force, resulting in wedging the sealing mechanism of the tip cap onto the luer of the container, and forming a tight seal due to the interference fit between the sealing mechanism and the luer. With the current tip caps, the torque required to attach and remove the tip cap is generated when the user applies a gripping force to the outside of the cap to rotate the cap on and off the syringe.
A problem associated with the prior art tip cap design has been the user must apply a gripping force to grasp the circular cap by exerting a force normal to the cap walls at the point of contact with sufficient force to hold the cap from slipping, as well as applying a twisting force (a torque) for rotating the cap about its axis. This can be difficult for some users who lack dexterity or strength especially considering the small size of the typical tip cap or in the case where the tip cap is in excessively tight engagement with the syringe barrel. The difficulty in using tip caps according to prior art design is that the user must exert forces on the tip cap at right angles to both grasp and rotate the tip cap simultaneously.
A need exists, therefore, for an improved syringe tip cap where the ability to attach and detach the tip cap is made easier by providing a tip cap that is easier to grip while simultaneously applying torque to rotate the tip cap. In particular, it would be advantageous to provide a tip cap with a non-circular shaped gripping surface that provides the user with a surface to grip the cap and apply force to the tip cap tangential to the axis of rotation without having to also apply a gripping force.